Embodiments of the present technology relate to aircraft altimeter systems. A radar or radio altimeter measures the distance between an aircraft and the ground, or structures on the ground such as buildings, trees, and the like, below the aircraft. Radar altimeter systems often use frequency modulated continuous wave (FMCW) radar techniques to determine the height of the aircraft above ground. Such a system generally transmits a signal whose frequency varies with time to the ground below the aircraft, receives the signal that is reflected back, and mixes or multiplies the received signal with a local oscillator signal that is related to the transmitted signal. The difference in frequency between the received signal and the local oscillator signal (derived from the mixing operation) may be used to determine the height above ground of the aircraft.